I finally installed my hybrid heat pump electric heater with a storage tank to increase hot water capacity to 80 gallons. I will upload actual pics but for now I wanted to get opinions if I need to change the way it's plumbed. I guess I'm doing this backwards. Take a look and let me know what you think. I have pressure relief valves on both units for safety. In the drawing the cold water from the house goes to the GE heater then the hot water from the GE unit in plumbed into the cold water inlet of the storage tank. The hot water outlet on the storage tank brings the hot water to all faucets, etc.

I have a taco that is plumbed to the drain valve (teed in with a drain valve) which pumps the water to the upper part of the GE tank. It is teed into the pressure relief valve.

It'll work the way you have it, but I'd think the GE tank will lag behind in coming up to temperature. (That might be a good thing) What turns the pump on & off? I think others might have plumbed it more like in my revised pic. That way both tanks are the same temp all the time. Either way, you'll have more capacity, but, recovery will be very slow. I understand the GE tanks have "standard" electric elements for when demand is high? Because of the extra tank & pump you might have just defeated the GE heat pump part & built a giant "standard" electric hot water tank. If so, then the way you have it plumbed may be the better way. Either way, if it has "standard elements" as well as the heat pump, I'd want to be able to "see" when they run. As I said, you might have just by passed the heat pump & forced it to run in expensive mode.

I think your way would work too. I decided. before seeing your drawing, that I wanted to be able to isolate the storage tank with valves. This way I can run the water heater with out the storage tank and if I see that I need more storage I can open the valves and have the extra capacity. Eventually I will put on a thermostat to turn on and off at the desired temp (not sure what that is yet)

Fred: The water heater has several options for making heat. THe operating modes are high demand, hybrid mode, E-heat and normal operation. E-heat is the only mode that uses the heat pump exclusively. I have the unit locked in that mode. Hybird uses the power hungry 4500 watt element and the heat pump. WIth 80 gallons of capacity I don't need any recovery for morning showers. I may also isolate the storage tank and run just the 50 gallon GE HWH alone but this is an experiment for the weekend. I don't want to be skinned alive by the women in my house.

Stand by loses for the total 80 gallons should be minimal. I need to insulate the pipes from each tank too. I also want to install a swich to turn on and off the Taco. If both tanks are at temperature the water doesn't need to circulate between the tanks.

In my furst drawing- I did plumb it out like this but had a leak where I teed the valve for the drain and the line that goes to the storage tank. I also couldn't figure out why it wasn't circulating the water between tanks. I had a valve shutoff that is very hard to see. ANyway, I like the newer setup better since the GE HWH looks to be on its own. If I need service the tech can't say that it's plumbed wrong. I still think the first scenario I had may have been slghtly better.

STUDY NoFossels design and maybe even draw it on a bar napkin -- then think like the water and draw with your crayon how the flow moves from tank to faucet.

--->Your designs expand the storage of the original tank

Thats all well and good but:

as you begin to use the stored energy it WILL be replaced with water that is street temperature -- 50(ish) degrees cold into BOTH tanks. or= Under hi demand the storage tank will be receiving new water at less than 120 degrees = as the system continues to circulate all the water stored in both tanks - the whole tank system will be mixed down to some lower temperature

WHY????

because the designs you have been shown and are drawing, provide no tank temperature stratification -

No FO, has created a design on his web site; as I posted, that (if) you use your geo heater in place of his boiler and your storage tank in place of his storage tank, then connect as his design - you regain tank stratification in both the production and the storage tank - and - AND - you gain a constant but not infinite supply of hot safe tap water.

The point Sting is making is that you have no stratification. All the water in both tanks will be the same temperature at any given time because the pump is constantly mixing it. Normally a hot water tank is such that hot water comes off the top, cold water goes in the bottom. As you use hot water, it stays about the same temp until the cold reaches the top and you run out of hot water. With your system as you use hot water, the temp will go down down down as you use it because the cold water entering is blended with the hot on an ongoing basis.

With out incorporating stratification into these two tank designs -- the economy of operation will be lost -- in fact it will cost more to operate the system than if the single tank system, were left alone in the first place.

I read your first post quickly. I have to really study the drawing you sent. I like the idea of being able to isolate the GE tank as I have it plumbed now. Anyway, I was just looking at the drawing I posted and it's not fully correct. I have the Taco pulling from the top of the storage tank (mostly hot water) where it gets pumped back top the top of the tank for the GE heater. Then the water is drawn from the bottom of the GE heater and is fed into the cold water inlet of the storage tank. I think this a better scenario then what I have pictured.

Maybe I'm looking at this wrong - when there is a call for hot water both tanks will help out with capacity and both will feed hot water from the tops of their tanks. Is this a better design?